Component stability structure

ABSTRACT

An electronic component assembly is described which comprises a stack of electronic components wherein each electronic component comprises a face and external terminations. A component stability structure is attached to at least one face. A circuit board is provided wherein the circuit board comprises circuit traces arranged for electrical engagement with the external terminations. The component stability structure mechanically engages with the circuit board and inhibits the electronic device from moving relative to the circuit board.

BACKGROUND

The present invention is related to an improved system for mountingelectronic components, and particularly multi-layered ceramic capacitors(MLCCs), to a circuit board. More specifically, the present invention isrelated to an improved system for mounting electronic componentassemblies to a circuit board while allowing for increased height towidth ratios thereby augmenting ongoing efforts related tominiaturization and space utilization.

Surface mount components become mechanically unstable when their heightto shortest width ratio exceeds about 3:1. Once this ratio of height towidth is exceeded the component may become unstable, or top heavy, andthe likelihood of toppling over during the assembly process, such asduring the solder reflow process, increases dramatically. Therefore, itis necessary for the component designer to follow basic design rules toensure that recommended height to width ratios are followed.Miniaturization within the electronics industry is forcing designers toconsider new approaches in designs that increase the volumetricefficiency of every component. Generally, miniaturization deals with thereduction in surface area the component consumes when mounted to acircuit board. This has led to a desire to utilize the vertical space,or Z-axis, extending perpendicular from the surface of the circuit boardthereby allowing small components to grow in height to at least theheight of the tallest component mounted on the circuit board. Space inthe Z-axis is typically under-utilized, primarily, because of the largenumber of defects and rework required to correct for toppled components.Designers have a long standing desire to maintain, or more preferablydecrease, the footprint of each electronic component assembly, definedas the surface area of circuit board occupied, while increasing theheight to maximize performance and overall volumetric efficiency.Unfortunately, these desires have been thwarted by conventional designstandards created to insure the component is structurally stable andthat it will not topple over with any induced shock or vibration duringassembly. The practitioner has therefore been in a design conundrum ofhaving to accept less volumetric efficiency or having to accept higherdefects neither of which is satisfactory.

It is also desirable to maintain the use of surface mount configurationsdue to the advantageous manufacturing and space considerations. Surfacemount configurations comprising solder pads wherein mating solder padson the circuit board and component are used to make both electrical andmechanical joints thereby eliminating the need for conductive leads thatextend through conductive vias in the circuit board.

In spite of past efforts, those of skill in the art still desire astructure which allows for increased height, perpendicular to the board,with decreases board footprint without the yield loss due to reworkcaused by mechanical instability due to the increased height. Animproved component stability structure is provided herein.

SUMMARY

It is an object of the invention to provide an improved componentstability structure for electronic component assemblies comprisingelectronic components, and particularly multi-layered ceramiccapacitors, which allows for increased height to width ratios, based onminimum width, with high yields and minimized circuit board reworkrequired.

A particular feature of the invention is the ability to provide acomponent stability structure which requires minimal circuit boardredesign, especially, with regards to the circuit trace designs.

These and other advantages, as will be realized, are provided in anelectronic component assembly comprising a stack of electroniccomponents wherein each electronic component comprises a face andexternal terminations. A component stability structure is attached to atleast one face. A circuit board is provided wherein the circuit boardcomprises circuit traces arranged for electrical engagement with theexternal terminations. The component stability structure mechanicallyengages with the circuit board and inhibits the electronic device frommoving relative to the circuit board.

Yet another embodiment is provided in a method for forming an electronicdevice comprising:

-   -   providing an electronic component assembly comprising:    -   a stack of electronic components wherein each electronic        component comprises a face and external terminations; and a        component stability structure attached to at least one face;    -   providing a circuit board comprising circuit traces arranged for        electrical engagement with the external terminations;    -   mechanically engaging the component stability structure with the        circuit board to inhibit the electronic device from moving        relative to the circuit board; and electrically connecting at        least one external termination of the external terminations to        at least one circuit trace.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an embodiment of the invention in front side schematic view.

FIG. 2 is the embodiment of FIG. 1 in right side schematic view.

FIG. 3 is the embodiment of the invention in right side schematic view.

FIG. 4 is an embodiment of the invention in front side schematic view.

FIG. 5 is an embodiment of the invention in front side schematic view.

FIG. 6 is an embodiment of the invention in top side schematic view.

FIG. 7 is an embodiment of the invention in front perspective schematicview.

FIG. 8 is an embodiment of the invention in front side schematic view.

FIG. 9 is an embodiment of the invention in front side schematic view.

FIG. 10 is an embodiment of the invention in front side schematic view.

DESCRIPTION

The present invention is directed to an improved component stabilitystructure suitable for use with electronic component assembliesparticularly comprising multiple electronic components, moreparticularly stacked electronic components and even more particularlyMLCC's, with a high height to width ratio based on the shortest width.More specifically, the present invention is related to a componentstability structure which allows for an increased volumetric density ofelectronic component assemblies, relative to the footprint, with no orminimal alteration of the circuit board and particularly no or minimalalteration of the electronic circuit traces of the circuit board.

The invention will be described with reference to the figures forming anintegral non-limiting component of the disclosure. Throughout thedescription similar elements will be numbered accordingly.

An electronic component assembly attached to a circuit board of anelectronic device is illustrated in schematic front side view in FIG. 1.In FIG. 1, the electronic component assembly, generally represented at10, comprises a plurality of electronic components, 12, which may be thesame or different wherein each electronic component has externalterminations, 14, of opposite polarity. Four electronic components areshown for the purposes of illustration without limit thereto. Eachelectronic component may independently represent a multilayered ceramiccapacitor comprising parallel electrodes with dielectric there betweenwherein adjacent electrodes terminate at external terminations ofopposite polarity as well known to those of skill in the art.Alternatively, each electronic component may independently have layerswhich form a resistor, an inductor, a thermistor, a fuse or anovervoltage protection component thereby providing resistivity,inductance, over-voltage arcing, fusing, variable resistance or otherfunctionality either singularly or in combination with otherfunctionality between external terminations. In particular, the presentinvention may provide multiple functions either in a single electroniccomponent, or in commonly stacked electronic components, such as a fuseand an MLCC or an over-voltage protection component and an MLCC, orother combinations. The face, 16, of the electronic component, which isnot part of the external electrical termination, is suitable forattachment of the component stability structure, 18, as will be morefully described herein. By attaching the component stability structureto the faces of the electronic components, wherein the face is an inertsurface, defined as a surface which does not contribute to electricalfunctionality, a portion of the component which is otherwise notutilized provides a mechanical function thereby allowing for improvedmounting capabilities without altering the electrical properties orphysical shape and size of the external termination or any lead frameattached thereto. An electronic component assembly can be prepared whichis surface mountable, with regards to electrical functionality, and alsomounted through the use of a component stability structure formechanical functionality.

With further reference to FIG. 1, the component stability structure, oran element of the component stability structure such as a pin, extendsperpendicular to the surface of the circuit board and into a, preferablyinert, via, 20, of the circuit board, 22. The pin may have across-sectional shape which is round, rectangular, oblong, obround,multi-faceted, such as a hexagon or octagon, or combinations thereof andmay be symmetrical or asymmetrical in cross-section. The via may extendinto or through the circuit board. An optional adhesive, 24, may securethe component stability structure in the via even though friction fit ora close proximity fit is preferred. The external terminations, 14, arein direct electrical contact with the circuit traces, 26, such as by asolder, 28, or a lead frame as will be more fully described herein.Direct electrical connection is defined herein as an electricalconnection without additional components wherein the two elements indirect electrical connection such as by a solder joint. In FIG. 1, theexternal termination is in direct electrical contact with the circuittrace.

The embodiment of FIG. 1 is illustrated in schematic right side view inFIG. 2 wherein an adhesive, 30, is illustrated whereby the componentstability structure is preferably adhered to each face wherein the facesare not visible in this view.

An embodiment of the invention will be described with reference to FIG.3 wherein the embodiment is illustrated in partial cut-away front viewwith a number of stacked components designed by the superscript integern. The number of components in the stack may be quite large andpreferably at least 2 to no more than 15 are suitable for demonstrationof the invention. More preferably, the number of stacked components is2-10 with 2-5 being most preferable. In FIG. 3, the component stabilitystructure, 18, comprises a multiplicity of pins, 181, which are receivedin, preferably, separate vias of the circuit board. It would be realizedthat one of skill in the art could utilize any number of pins on eachcomponent stability structure.

An embodiment of the invention will be described with reference to FIG.4 wherein the embodiment is illustrated in right side schematic view. InFIG. 4, the component stability structure, 18, comprises a foot, 32,extending parallel to the surface of the circuit board, 22, and restingon the surface of the circuit board as opposed to a pin extending into avia of the circuit board. The component stability structure can be incontact with the circuit board surface without adhesive or may beadhered to the surface by an adhesive. The foot provides mechanicalstability by mechanical engagement with the circuit board therebyinhibiting the electronic component assembly from moving relative to thecircuit board. Mechanical engagement of the foot or pin can be by anadhesive, by frictional resistance to movement or by a catch mechanismas described further herein to include a physical transformation of thepin such as a bend or an engagement with a land. A lead frame, 35, inelectrical contact with, preferably, all external terminations of commonpolarity is in electrical contact with a circuit trace, 26, such as by asolder bond, 28. The mechanical engagement between the componentstability structure occurs prior to electrical engagement and may remainor the component stability structure may be removed after electricalengagement is complete.

An embodiment of the invention will be described with reference to FIG.5 wherein the component stability structure, 18, extends around thestack of electronic components thereby forming a partial encasement. Astability protrusion, 34, extends from the component stability structureand secures the stack of electronic components in the partial encasementthereby potentially eliminating any adhesive between the face andcomponent stability structure. A stability protrusion can be used oneither side thereby providing a component stability structure which canbe flexed open, the stack inserted, and the component stabilitystructure allowed to relax with the stack of electronic componentsphysically secured therein.

An embodiment of the invention is illustrated in top schematic top viewin FIG. 6. In FIG. 6, the component stability structure, 18, is an anglemounted such that the long dimension is perpendicular to the circuitboard. The component stability structure provides lateral supportthereby inhibiting the stack from tipping in either direction. Dependingon the application, and particularly time between placement andsoldering, the component stability structure may be secured to thecircuit board, such as by an adhesive, or gravity and lack of motion maybe relied upon for the stack of electronic components to remain in placeuntil soldering and electrical contact can be established. The componentstability structure has no electrical function and therefore thefootprint of the component assembly can be enlarged, as in FIG. 6,without electrical interference issues. Therefore, unlike lead frames,the component stability structure of adjacent component assemblies canbe quite close, and even in contact, without detriment.

An embodiment of the invention is illustrated in side perspective viewin FIG. 7. In FIG. 7, the component stability structure, 18, comprises afoot, 32, wherein a pin, 182, is punched from the component stabilitystructure.

Embodiments of the invention are illustrated in schematic side view inFIGS. 8-10 wherein mechanical constraints or clips are illustrated. Ineach figure an electronic component assembly, 10, comprising a stack ofelectronic components, 12, between component stability structures, 18,secured by adhesive, 30, is illustrated. Extended pins, 46, areillustrated wherein extended pins are defined herein as pins that extendthrough the via, 20, and protrude at least partially through the circuitboard, 22. In FIG. 8 the extended pins are crimped inboard, or towardseach other whereas in FIG. 9 the extended pins are crimped outboard.Each electronic component assembly may comprise a single extended pin ormultiple extended pins. The length for the crimped pin design ispreferably the board thickness plus about 0.254+/−0.0127 cm(0.100+/−0.005 inches), this length can be varied to accommodateequipment clinching capabilities.

An embodiment of the invention is illustrated in partial schematic viewin FIG. 10. In FIG. 10 the pin, 183, comprises a catch, 50, extendingfrom the termination of the pin at an angle. The circuit board orsubstrate, 22, comprises a primary bore, 52, and a larger secondarybore, 54, intersecting the primary bore and opposite the side on whichthe electronic component assembly is to be mounted. The pin ispreferably flared towards the catch and the catch, 50, is sufficientlysmall to traverse the primary bore and when entering the secondary borethe catch engages the land, 56, thereby securing the device in position.In one embodiment the primary bore can be formed by drilling a firsthole through the substrate with the secondary bore formed thereafterwith a larger drill passing only partially through the circuit board andat least overlapping the primary bore. Alternatively, the catch can passthrough the substrate and engage the face of the substrate opposite thecomponent wherein the face functions as a land.

The component stability structure allows the component designers to takeadvantage of the space above the circuit board to maximize thecomponent's volumetric efficiency by increasing the height of acomponent while maintaining or reducing its footprint or surface areathat it consumes on the circuit board. The component stability structureprovides mechanical support for various types of component designs. Thecomponent stability structure is particularly suitable for use withsurface mount components having high width to height aspect ratios. Thecomponent stability structure can be applied to stacks of components,and preferably MLCC's, that have height to width ratios exceeding 2:1,more preferably exceeding 3:1 and even more preferably exceeding 4:1.Though not limited herein the height to width ratio for most circuitdesigns, based on other considerations, is limited to about 10:1.

The component stability structure comprising a material selected frommetal, plastic and a temporary material. Non-conductive materials arepreferred, though not required, as non-conductive materials,particularly plastics, are typically lower cost and lighter weight.Temporary materials are materials which can be removed by thermaltreatment, optical treatment or chemical treatment and are particularlysuitable as they can be utilized to secure the component assembly inplace and the removed after the component is secured. Particularlysuitable removable materials include thermoplastics.

The component stability structure may be attached to the face of theelectronic component by an adhesive such as an epoxy, an acrylate orsilicone adhesive.

The invention has been described with particular reference to preferredembodiments without limit thereto. One of skill in the art would realizeadditional embodiments and improvements which are not specificallyenumerated but which are within the scope of the invention asspecifically set forth in the claims appended hereto.

The invention claimed is:
 1. An electronic component assemblycomprising: a stack of electronic components wherein each electroniccomponent of said electronic components comprises a face and externalterminations wherein said face comprises an inert surface; a componentstability structure attached to said inert surface; a circuit boardcomprising circuit traces arranged for electrical engagement with saidexternal terminations; wherein said component stability structuremechanically engages with said circuit board and inhibits saidelectronic component from moving relative to said circuit board; whereinsaid component stability structure does not contribute to electricalfunctionality; and wherein said stack of electronic components furthercomprises at least one solder joint in directly electrical contact withat least one said external termination of said external terminations andat least one circuit trace of said circuit traces.
 2. The electroniccomponent assembly of claim 1 wherein at least one said electroniccomponent is a multilayered ceramic capacitor comprising parallelinternal electrodes with dielectric there between wherein adjacentinternal electrodes are in electrical contact with separate saidexternal terminations.
 3. The electronic component assembly of claim 1wherein at least one said electronic component is selected from thegroup consisting of a resistor, an inductor, a thermistor, a fuse and anovervoltage protection component.
 4. The electronic component assemblyof claim 1 wherein said stack of electronic components comprises atleast 2 said electronic components.
 5. The electronic component assemblyof claim 1 wherein said component stability structure comprises a footextending parallel to a surface of said circuit board.
 6. The electroniccomponent assembly of claim 1 wherein said component stability structurecomprises a pin extending perpendicular to a surface of said circuitboard.
 7. The electronic component assembly of claim 1 wherein saidcomponent stability structure comprises a foot extending parallel to asurface of said circuit board and a pin extending perpendicular to saidsurface of said circuit board.
 8. The electronic component assembly ofclaim 1 wherein said component stability structure comprising a materialselected from metal, plastic and a removable material.
 9. The electroniccomponent assembly of claim 1 further comprising an adhesive betweensaid component stability structure and said circuit board.
 10. Theelectronic component assembly of claim 1 wherein said componentstability structure comprising a non-adhesive constraint.
 11. Theelectronic component assembly of claim 1 wherein said componentstability partially encases said stack of electronic components.
 12. Theelectronic component assembly of claim 1 wherein said componentstability structure further comprises at least one stability protrusion.13. The electronic component assembly of claim 4 wherein said stack ofelectronic components comprises no more than 15 of said electroniccomponents.
 14. The electronic component assembly of claim 6 whereinsaid pin extends at least into a via of said circuit board.
 15. Theelectronic component assembly of claim 6 wherein said pin has across-sectional shape selected from round, rectangular, oblong, obround,multi-faceted, such as a hexagon or octagon, or combinations thereof.16. The electronic component assembly of claim 8 wherein said componentstability structure comprises a thermoplastic.
 17. The electroniccomponent assembly of claim 9 wherein said adhesive is selected from thegroup consisting of epoxies, acrylates, silicones.
 18. The electroniccomponent assembly of claim 10 wherein said non-adhesives constraint isselected from a compressive mechanical constraint and a clip.
 19. Theelectronic component assembly of claim 13 wherein said stack ofelectronic components comprises at least 2 to no more than 10 of saidelectronic components.
 20. The electronic component assembly of claim 14wherein said via is an inert via.
 21. The electronic component assemblyof claim 14 wherein said via comprises a land.
 22. The electroniccomponent assembly of claim 14 wherein said pin comprises a crimp. 23.The electronic component assembly of claim 19 wherein said stack ofelectronic components comprises at least 2 to no more than 5 of saidelectronic components.
 24. The electronic component assembly of claim 22wherein said pin comprises a catch.
 25. The electronic componentassembly of claim 22 wherein said pin comprises a catch engageable witha land of said circuit board.
 26. The electronic component assembly ofclaim 25 wherein said land is in said via.
 27. An electronic componentassembly comprising: a stack of electronic components wherein eachelectronic component of said electronic components comprises a facecomprising an inert surface, and external terminations wherein saidinert surface is not part of said external termination; a componentstability structure attached to said inert surface; a circuit boardcomprising circuit traces arranged for electrical engagement with saidexternal terminations; wherein said component stability structuremechanically engages with said circuit board and inhibits saidelectronic device from moving relative to said circuit board; andwherein said component stability structure does not contribute toelectrical functionality; and wherein said stack of electroniccomponents further comprises at least one solder joint in directlyelectrical contact with at least one said external termination of saidexternal terminations and at least one circuit trace of said circuittraces.